Explanations:Understanding the correct usage of prepositions with time is a fundamental aspect of English grammar. Prepositions are words that indicate the relationship between a noun or pronoun and other parts of the sentence. In the context of time, different prepositions are used depending on the specificity of the time being referred to.
When referring to specific times, such as hours and minutes, the preposition "at" is used. For example, "The train leaves at 3:00 pm" and "The train reaches at 7:00 pm" are correct. The preposition "at" is appropriate for specific points in time, such as exact hours, minutes, or seconds.
On the other hand, the preposition "on" is used for days and dates. For instance, "The meeting is on Monday" or "The event is on January 1st." The preposition "on" is used to indicate a specific day or date within a larger time frame.
The preposition "in" is used for larger time periods such as months, years, and seasons. For example, "The festival is in December" or "The project will be completed in 2024." The preposition "in" is used to indicate a time period that is not as specific as a particular day or hour.
It is important to note that using the wrong preposition can lead to confusion and miscommunication. For instance, saying "The train leaves on 3:00 pm" would be incorrect because "on" is not used for specific times. Similarly, saying "The train leaves in 3:00 pm" would also be incorrect because "in" is not used for specific times either.
Therefore, the correct answer is "at" for both the departure and arrival times in the given sentence. The sentence "The train leaves Delhi at 3:00 pm and reaches Chandigarh at 7:00 pm" is grammatically correct and clearly conveys the specific times of departure and arrival.